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Date: Sat, 9 May 2015 17:29:11 +0530
From: Vinod Koul <vinod.koul@...el.com>
To: Robert Jarzmik <robert.jarzmik@...e.fr>
Cc: Jonathan Corbet <corbet@....net>, Daniel Mack <daniel@...que.org>,
Haojian Zhuang <haojian.zhuang@...il.com>,
dmaengine@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 3/5] dmaengine: pxa: add pxa dmaengine driver
On Fri, May 08, 2015 at 02:28:37PM +0200, Robert Jarzmik wrote:
> Vinod Koul <vinod.koul@...el.com> writes:
>
>
> >> +#define DRCMR_MAPVLD BIT(7) /* Map Valid (read / write) */
> >> +#define DRCMR_CHLNUM 0x1f /* mask for Channel Number (read / write) */
> >> +
> >> +#define DDADR_DESCADDR 0xfffffff0 /* Address of next descriptor (mask) */
> >> +#define DDADR_STOP BIT(0) /* Stop (read / write) */
> >> +
> >> +#define DCMD_INCSRCADDR BIT(31) /* Source Address Increment Setting. */
> >> +#define DCMD_INCTRGADDR BIT(30) /* Target Address Increment Setting. */
> >> +#define DCMD_FLOWSRC BIT(29) /* Flow Control by the source. */
> >> +#define DCMD_FLOWTRG BIT(28) /* Flow Control by the target. */
> >> +#define DCMD_STARTIRQEN BIT(22) /* Start Interrupt Enable */
> >> +#define DCMD_ENDIRQEN BIT(21) /* End Interrupt Enable */
> >> +#define DCMD_ENDIAN BIT(18) /* Device Endian-ness. */
> >> +#define DCMD_BURST8 (1 << 16) /* 8 byte burst */
> >> +#define DCMD_BURST16 (2 << 16) /* 16 byte burst */
> >> +#define DCMD_BURST32 (3 << 16) /* 32 byte burst */
> >> +#define DCMD_WIDTH1 (1 << 14) /* 1 byte width */
> >> +#define DCMD_WIDTH2 (2 << 14) /* 2 byte width (HalfWord) */
> >> +#define DCMD_WIDTH4 (3 << 14) /* 4 byte width (Word) */
> >> +#define DCMD_LENGTH 0x01fff /* length mask (max = 8K - 1) */
> > Please namespace these ...
> Sorry I don't get this comment, would you care to explain me please ?
Right now you are using very genric names which can conflict with others, so
makese sense to add PXA_DCMD_LENGTH with me lesser prone to conflicts rather
than DCMD_LENGTH
>
> >> +#define _phy_readl_relaxed(phy, _reg) \
> >> + readl_relaxed((phy)->base + _reg((phy)->idx))
> >> +#define phy_readl_relaxed(phy, _reg) \
> >> + ({ \
> >> + u32 _v; \
> >> + _v = readl_relaxed((phy)->base + _reg((phy)->idx)); \
> >> + chan_vdbg(phy->vchan, "readl(%s): 0x%08x\n", #_reg, \
> >> + _v); \
> >> + _v; \
> >> + })
> >> +#define phy_writel(phy, val, _reg) \
> >> + do { \
> >> + writel((val), (phy)->base + _reg((phy)->idx)); \
> >> + chan_vdbg((phy)->vchan, "writel(0x%08x, %s)\n", \
> >> + (u32)(val), #_reg); \
> >> + } while (0)
> >> +#define phy_writel_relaxed(phy, val, _reg) \
> >> + do { \
> >> + writel_relaxed((val), (phy)->base + _reg((phy)->idx)); \
> >> + chan_vdbg((phy)->vchan, "writel(0x%08x, %s)\n", \
> >> + (u32)(val), #_reg); \
> >> + } while (0)
> >> +
> >> +/*
> > ??
> > Does this code compile?
> Oh yes, it compiles and works with both debug on and debug off. This is actually
> the most handy debug trace of this driver. I've been using that kind of
> accessors for years in my drivers, and this is truly something I need to
> maintain the driver, especially when a nasty corner case happens on a hardware I
> don't own.
You have start of comment on that line, no ending, so how does it compile!
> >> + spin_lock_irqsave(&pdev->phy_lock, flags);
> >> + for (prio = pchan->prio; prio >= PXAD_PRIO_HIGHEST; prio--) {
> >> + for (i = 0; i < pdev->nr_chans; i++) {
> >> + if (prio != (i & 0xf) >> 2)
> >> + continue;
> >> + phy = &pdev->phys[i];
> >> + if (!phy->vchan) {
> >> + phy->vchan = pchan;
> >> + found = phy;
> >> + goto out_unlock;
> > what does phy have to do with priorty here?
> Each phy has a priority, it's part of the hardware. IOW each phy has a "granted
> bandwidth". This guarantee is based on the number of request on the system bus
> the DMA IP can place.
>
> In PXA2xx/PXA3xx, the DMA IP can have 8 simulaneous request. The highest
> priority phys always get 4 slots, the high 2 slots, etc ...
>
> So a priority is an intrinsic property of a phy.
Yes that part is ok, but why are you looking up priorty while searching for
a phy, searching thru number of channels should suffice?
> >> +static struct pxad_desc_sw *
> >> +pxad_alloc_desc(struct pxad_chan *chan, unsigned int nb_hw_desc)
> >> +{
> >> + struct pxad_desc_sw *sw_desc;
> >> + dma_addr_t dma;
> >> + int i;
> >> +
> >> + sw_desc = kzalloc(sizeof(*sw_desc) +
> >> + nb_hw_desc * sizeof(struct pxad_desc_hw *),
> >> + GFP_ATOMIC);
> >> + if (!sw_desc) {
> >> + chan_err(chan, "Couldn't allocate a sw_desc\n");
> > this is not required, memory allocator will spew this as well. I think
> > checkpatch should have warned you..
> Checkpatch did not, but I agree, will remove this print alltogether. For v3.
surprised it does actually, see,
# check for unnecessary "Out of Memory" messages
>
> >> +static enum dma_status pxad_tx_status(struct dma_chan *dchan,
> >> + dma_cookie_t cookie,
> >> + struct dma_tx_state *txstate)
> >> +{
> >> + struct pxad_chan *chan = to_pxad_chan(dchan);
> >> + enum dma_status ret;
> >> +
> >> + ret = dma_cookie_status(dchan, cookie, txstate);
> > pls check if txstate is valid
> My understanding is that's already the job of dma_cookie_status() and
> dma_set_residue().
Yes it is, but is txstate is NULL then no need to calculate residue so bail
out here
--
~Vinod
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